imo, spark plugs don't make horsepower. If they are of the proper heat range they will self clean. And if they are made of quality material and designed correctly for the application they will physically hold up... So its about having the proper plug for the application that's important. Anyway thats how i see it.

The way the various spark plug manufacturers number their plugs makes it a bit of a challenge to nail the plug you want for your specific engine. Plus one manufacturer heat range doesn't cross exactly to another's as they seem to overlap some. Either a little hotter or colder. My recommendation is to use a cheap plug to determine heat range. Then when you are close go to the plug of your choice. Using Champions the stock range is 4, going one step colder is 5. This should be a good plug except for those with power adders. 2 steps colder should include the majority of power adders. 3 steps colder for high compression with big power adders. Then when the heat range and characteristics are determined. Then install the best quality plug you can find that give you these qualities. Anyhow thats my approach, keeping in mind each engine is different. Good luck..